The invention relates to an ice slurry distributor for a freezing apparatus. More particularly, the invention relates to an ice slurry distributor for a falling film ice crystallizer which is used in the treatment of an effluent waste stream.
Effluent wastes, such as those emitted by pulp mills, can be treated by freezing to form a slurry of pure crystallized water and liquid waste. The crystallized water is separated from the liquid waste and then recovered.
A falling film ice crystallizer is an indirect heat exchanger, which generally comprises an ice slurry distributor at the top, for distributing the slurry to a heat exchange apparatus below, and a receiver, located below the heat exchange apparatus, for collecting a slurry containing frozen product and concentrated liquid. A portion of the collected slurry is fed to a separation apparatus and a portion is recycled to the distributor.
In a falling film heat exchanger, a large quantity of fluid flows down and across the heat transfer area. In commercial equipment where a large recirculation flow (100 to 1000 m.sup.3 /hr) is often used, the slurry must be efficiently and uniformly distributed to the heat transfer elements, which are tubes in the case of tubular type falling film exchangers.
The slurry should be efficiently distributed to the heat exchange element so that the element does not foul or become starved of adequate fluid flow. In the case of ice slurries and other slurries where solids are lighter than the liquid, the distribution of the slurry must be gentle to prevent separation and breakage of the ice crystals or solids. In addition, the ice slurry should be distributed to the heat exchange element quickly to maintain homogeneity of the slurry.
In contrast to prior art distributors, the invention meets these requirements with a minimum attrition of crystals and without expending excessive energy.